This invention relates generally to a piston stroke control, and more specifically to a variable frequency control for a percussion actuator.
U.S. Pat. No. 3,995,700 issued to Mayer et al. discloses a hydraulic rock drill system in which the frequency of a hammer stroke is controlled by adjusting the pressure required for a closure member to open. The stroke frequency is thus altered by changing the period required by the hammer to respond to the opening of a valve. In comparison, the instant invention alters the stroke of the piston by changing the period required for the valve to complete its motion once the motion has begun.
U.S. Pat. No. 4,425,835 issued to Krasnoff discloses a fluid actuator involving a piston 28, and a valve 36. The valve controls the pressure exerted on the piston. The amount of pressure existing in cushion chamber 14 determines how quickly the valve will respond to the any motion of the piston 28.
The Krasnoff valve does not affect the time it takes from when the valve is moved from the at rest position to the position at which the pressure is effectively switched to the piston, as is the case in the instant invention.
The forgoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.